The first rudimentary electrical connectors that could be connected and disconnected underwater appeared in the mid-1960's, with reliable commercial products not becoming available until the mid-1980's. Prior to that time, subsea systems had to be fully connected electrically before submersion. In the intervening years many Offshore Industry applications have been developed that require electrical elements to be repeatedly connected and disconnected while immersed in seawater. There are several known devices that fulfill that requirement. A subset of such devices comprises connectors wherein the electrical contacts consist of pins and sockets to be joined in a chamber filled with a benign substance that protects them from the external environment. The protective substance, a mobile dielectric material such as oil, grease, or gel, hereinafter referred to simply as fluid or oil, is pressure-balanced to ambient in-situ conditions by way of a compensating element which is typically a flexible wall of the chamber in which it is housed. Representative examples of the prior art can be found in U.S. Pat. Nos. 3,508,188; 3,522,576; 3,643,207; 4,085,993; 4,142,770; 4,373,767; 4,795,359; 4,948,377; and 5,171,158.
In this subset of prior-art underwater connectors the pins generally have elongated electrically-conductive shafts that are coated with dielectric sheaths, and have exposed electrically conductive contact tips. The pins enter the contact chamber by way of penetrable end-seal passages that are intended to remain sealed from the outside environment before, during, and after mating and de-mating. Once mated, the conductive pin-tips are completely immersed within the contact chamber, leaving a portion of the electrically insulated shafts exposed to the in-situ environment. For ease of discussion, the connector unit in which pins are housed shall hereafter be referred to as the “plug,” and the unit housing the sockets within the mating chamber shall be referred to as the “receptacle.”
It is a challenge to keep the receptacle end-seal passages leading into the oil chamber closed before, during, and after mating and de-mating. To meet that challenge, connectors that represent this subset and are currently commercially available have evolved into complex devices having plug pins with circular cross sections, and receptacles with resilient end-seals having circular, re-sealable passages to accept the respective cylindrical pins. Currently on the market there are connectors employing one or the other of two different approaches for keeping the cylindrical, bore-like end-seal passages sealed at all times.
In the first approach, when the connector portions are unmated the elastomeric receptacle end-seal passages are occupied by rigid, non-electrically-conductive, cylindrical stoppers housed within the mating chamber. The stoppers are biased outward by robust springs. During mating, the entering plug pins force the stoppers inward beyond the end-seals and further into the mating chamber, thereby compressing the springs. The result is that the receptacle mating-chamber end-seal passages are always occupied, either by the stoppers when unmated, or by the plug pins when mated. That keeps the circular end-seal passages always sealed from the outside environment, but it does so at the expense of a great deal of complexity. The springs must be robust to guarantee reliable return of the stoppers into the end-seal passages upon demating. That creates substantial mating forces, and requires a latching mechanism or other means to keep the connector portions from springing apart once mated. And even though the return springs are robust, failures occasionally occur when the spring-driven stoppers fail to return outward into the end-seal passages. That leaves a leak path between the chamber fluid and the in-situ environment. A representative example of this sort of connector is found in U.S. Pat. No. 4,948,377.
The second, less reliable approach to the circular end-seal closure challenge is to pinch resilient, tubular, end-seal passages closed when the connector portions are unmated. The force required to keep the circular tubular passages pinched closed is provided either by an elastomeric sphincter surrounding the passage, or by a metal spring, or by both a spring and an elastomeric sphincter acting together. Upon mating, the pinched tube is forced open by a slender, tapered end of the circular cross-section incoming plug pin; thus remaining sealed against the plug pin's surface during mating and de-mating, and while mated. One example of this sort of connector is found in U.S. Pat. No. 4,373,767. The invention has no stoppers or stopper-biasing springs, and therefore is mechanically much simpler than connectors built around the concept mentioned in section [005]. It has major disadvantages however: the substantial force required to pinch a circular end-seal passage completely closed makes mating and de-mating difficult, sometimes resulting in tearing of the tubular passage, and subsequent failure. The construction has the further disadvantage of failure of the circular tubular passages to close properly after prolonged mating at cold temperature. When that happens a leak path is created between the chamber oil and the in-situ environment, for instance electrically conductive seawater. In addition, the high stress required of such end-seals is detrimental to the seal's elastomeric properties. All of these disadvantages compromise the reliability of this sort of connector.
There is third, completely different, approach which is not currently on the market. The early technology disclosed in U.S. Pat. No. 3,643,207 approached the connector seal-closure problem in a much less complex way. Instead of attempting to keep circular bore-shaped resilient passages closed, it employed one narrow, slitted passage through an elastomeric receptacle end-seal for each respective one blade-like plug pin. Little or no end-seal material was removed in creating the slits. A slit is much easier to keep closed than a cylindrical bore because it is closed in its natural unstressed condition. A blade-like pin causes little distortion of a properly-sized slitted opening, and only slight stress on the elastomeric seal material. Although the blade-in-slit sealing concept itself is very sound, connectors incorporating that approach lacked the necessary attributes to function reliably. For example, the only mechanism provided to close the slits was the elasticity of the resilient end-seal material through which the slits were cut. Upon demating after prolonged mating at cold temperatures the slits closed very slowly, allowing a temporary leak path between the chamber fluid and the in-situ environment. When that happened, the chamber fluid became contaminated by intruding environmental fluid such as seawater, thereby degrading its electrical properties. No positive means were included to isolate conductive elements within the chamber fluid from each other, so intruding contaminants occasionally caused electrical circuit-to-circuit internal breakdown. For those and other reasons the concept was abandoned years ago in favor of the aforementioned more complex approaches.
In addition to the fact that all of the aforementioned products have some technical shortcomings, the complexity and expense of the underwater connectors described in paragraphs [005] and [006] puts them out of reach of many, if not most, harsh environment projects. Those described in paragraph [007] never resulted in viable commercial products. What is still needed is a connector device that reduces or overcomes the shortcomings found in the known harsh environment connectors as described above, while simultaneously reducing the complexity and cost of manufacture. This invention fulfills that need.